Just the other day, I put in a Aluminum Driveshaft to replace my stock driveshaft (mainly because of the vibration at highway speeds I was getting)...also replaced the output seal, but...for some reason, my car WILL NOT, CAN NOT, & JUST WONT chirp 2nd anymore???? Has done it since the day I have owned it until now. Anyone know why this happened. Everything feels good and tight just curious, did I lose Horsepower putting this in and is this what is suppose to happen. Does it have to do with the Aluminum one having a larger diameter which makes it have to do more revolutions?just a guess

 

same revs, you shouldn't lose any power
is your fluid full?
I don't like aluminum driveshafts

 

Fluid topped off w/ 75w-90 mobile 1 synthetic and the GM limited slip additive, im seriously stumped......i may not like them anymore either if I cant figure out what is going on, lol

 

Thats scary because i just bought an aluminum DS off ebay to replace my vibrating steel one. I'll let you know how my test-drive turns out. Also should i replace my seals and is it easy to do? The front of my differential is covered in oil and gunk but my diff fluid levels are ok. i've always thought i had a bad rear seal.

 

If anything it should free up power. There are dyno results showing a few horse and ft/lbs at the wheels from switching over. I never noticed a loss of power with mine.

-Dustin-

 

Yeah, let me know what happens after the install and truthfully, your in there so you might as well replace the seal while you have it out, the one i replaced was the trans. output seal though, it was really messed up and actually could have been causing some of my vibrations, but I have not yet tested it out at high speeds yet, which is when mine would vibrate. Oh and if your diff. fluid levels are ok, then maybe its a leak from somewhere else. i know that when going highways speeds for some time, a leak from the oil pan, rear main seal, ect... will cover pretty much everything in oil, just a thought

 

thats what i thought would happen...car doesnt "seem" slower, it just wont chirp 2nd anymore, i just cant figure it out

 

An aluminum drive shaft would be lighter then the steel one and reduce the rotating mass. There shouldn't be any loss of HP.

Sick97SS he has an auto trans. Yours should still chirp 2nd and 3rd since you have an M6

 

I know its lighter, but seriously, not by much, I held both and didnt really notice "too" much of a difference. it has to be within like 5 lbs. at most. But, does the lower rotating mass equal out with the fact that the aluminum one is wider?

If no HP loss then why no chirp, not saying your wrong just trying to figure this out

 

anyone have any ideas

 

Are you sure nothing else has changed?
Dirty air filter?
Change in temperature?

I've installed those in quite a few cars without problems.
You could always switch back and see what happens.

 

EDIT: <<<This below explanation of chirp is applied incorrectly with respect to the driveshaft effects, since the driveshaft is 'downstream' of the clutch. Please see subsequent posts which point this out. I'll use the 'no coffee in bloodstream yet' excuse this time. JP>>>

Chirp is achieved due to the kinetic energy of the drivetrain, spinning at a higher RPM than needed for a given speed/gear, being suddenly dumped to the wheels. That kinetic energy gives you a brief but large torque spike while the clutch is engaging and pulling the revs down. That torque spike is limited by the capacity of the clutch, not the torque of the engine. So, if you lighten the rotating inertia significantly, it will be harder to chirp the tires. As you mentioned this has to do with the diameter in the case of the driveshaft; it's not really the mass(weight), but the moment of inertia, that counts.

I don't really know, but I doubt if the aluminum DS moment of inertia is significantly lower than stock. Moment of inertia is dependant on the mass times the SQUARE of the radius the mass is rotating about. So, a small increase in diameter can offset a significant mass reduction pretty quickly.

 

My thoughts exactly,lol j/k but i think I understand ....So, pretty much what im getting from this and others is that because of the fact that the DS is aluminum, its wider, and has more flex, then those things are what is keeping my car from chirpin 2nd which would mean I did not lose HP. sound close

Really, I am just curious if anyone that was chirpin 2nd in thier auto, after installing the DS couldnt anymore

 

with 4.10 gears and a 3k stall converter Im sure your car would chrip second... maybe third

 

If nothing else changed (weather,tire pressure, etc.) then I would also say it due to the loss of inertia. Also the steele DS has a 5in steele damper on the trans side which can "spring load" the drive shaft. An aluminum DS does not have the damper nor will it spring load like steele. You may have lost some coolness factor not being able to chirp the tires but traction loss slowes you down.


Kevin